The roles of esterified and unesterified cholesterol in the intestinal chylomicron will be examined in mesenteric lymph and bile fistula rats. In particular, we will determine the extent to which chylomicron cholesterol esterification can be suppressed by high rates of triglyceride transport, especially in animals lacking two major sources of luminal cholesterol, bile and diet. If an obligatory small fraction of CE is found its source will be traced. Studies of the enzyme lecithin:cholesterol acyl transferase (LCAT) in intestinal lymph will be continued to determine its specific activity in various apoprotein fractions, especially lymph HDL and subfractions of HDL apoprotein. The inhibitors of serum LCAT present in intestinal lymph VLDL and serum and HDL apoproteins will be further characterized. Lymph from other organs, particularly rat liver, and from other species will also be examined for LCAT inhibitory factors.